Damaged oil wells releasing uncontrolled flows of geopressured oil and gas represent a significant loss of revenue as well as a fire and environmental hazard. The key to controlling the flow from a damaged oil well which is on fire is to divert, or at least tolerate, the flame front emanating from the wellhead while effectively corking the wellhead and stopping the subsequent flow of oil and gas therefrom, thus "snuffing" or "killing" the fire by removing its source of fuel.
In many cases, such as in the oil fields in Kuwait, there is either strong geologic overpressure at the wellhead and/or a substantial dynamic gas pressure which causes the oil to "gush" from the well, sometimes with considerable force. For a typical 3.5-inch diameter production well pipe, this upward-driving force may reach as much as 70,000 lb., or even higher. As a result, the "cork" must be strongly anchored and, frequently, be quite heavy.
To be effective, a well capper and fire "snuffer" should perform the following five separate functions: (1) divert the flame front or tolerate it if fire is present; (2) find the bent and twisted wellhead pipe opening; (3) exert a downward capping force greater than that of the upward geologic and gas pressure forces so as to penetrate the pipe and halt the oil and gas flow; (4) seal the wellhead pipe against leakage; and (5) allow mud to be pumped into the well pipe until the well pressure equals or balances the geopressure or earth's own pressure thus "killing" the well for subsequent repair and maintenance. Once flow control repair work is completed, simply removing the mud will allow production to be resumed safely.
Prior art practices for capping an out of control oil well require extinguishing the fires by removing the combusting air from the escaping fuel. In one method this is accomplished by detonating explosives placed to create a shock wave and oxygen starved air which act to remove oxygen from around the fire. Another method involves injecting liquid nitrogen into and around the the oil/gas stream from the wellhead using a "stove pipe", to accomplish the same result. Since neither approach stops the flow of oil and gas from the wellhead, it is most important that the ground surrounding the burning well be thoroughly cooled with water and that any hot debris or wreckage be removed to prevent the spontaneous reignition of the gushing oil and gas. At least 100,000-1,000,000 gallons of water per well site is typically required to accomplish such cooling, and the water, generally speaking, cannot be recovered. In a desert area, such as the Arabian peninsula and in a number of other Middle Eastern oil fields, reliably providing such amounts of water can often be a significant problem.
Once the fire is extinguished, a packer or "capper" is placed in the well bore and secured by clamping the packer to a flange on the wellhead pipe. Due to the high well pressures and the highly combustible nature of the oil and gas mixture flowing from the wellhead pipe, such capping of the freely flowing oil and gas stream is quite hazardous and requires highly skilled personnel to accomplish. One inadvertent spark can rekindle the fire of the flow stream and oil pooled on the ground surrounding the well. Furthermore, as in the Kuwait oil field, the wellhead pipes and connecting flanges are often destroyed making the well capping by a conventional packer nearly impossible.
Finally, drilling mud is pumped into the well to fill the well pipe and shut off the oil and gas flow therefrom. The packer can then be removed and repairs made on the non-flowing well. Alternatively, the necessary repairs may be made on the pressurized well capped by the packer.
Thus, there is a need for (1) improved oil well capping and fire snuffing apparatus which is free standing and does not require attachment or clamping to a damaged or missing wellhead pipe and (2) improved and simplified methods for more quickly, safely and inexpensively extinguishing oil well fires while using much less water and being able to recover and reuse the water. The present invention satisfies such needs.